We are currently conducting a perspective evaluation of the role of diabetic blood glucose control in the development of microvascular disease and accelerated macrovascular disease in juvenile onset diabetic patients. Diabetic control is being evaluated by serial measurements of glycosylated hemoglobins (Hgb A1 a+b+c) at two month intervals, which provide an accurate integrated index of blood glucose levels over an extended period of time. Microvascular disease is assessed by the rate of progrssion of quadriceps capillary basement membrane thickness (CBMT) obtained on muscle biopsies at the beginning of the study, two and four years later. The traditional risk factors for the development of macrovascular disease in this population are being measured and correlated with the various parameters of diabetic control. This proposal will analyze platelet function in this well characterized group of juvenile onset diabetics. The study will determine the nature and presence of platelet function abnormalities to the other parameters being measured in this population (i.e. glycosylated hemoglobin, capillary basement membrane thickness, plasma lipids, etc.). We will seek to determine the relationship of various parameters of diabetic blood glucose control to these platelet abnormalities, and more specifically analyze the role of the prostaglandin endoperoxide production pathway in the abnormal platelet function noted in these patients. In addition, this proposal seeks to strengthen the existing data management system developed for this study by providing additional personnel to facilitate data entry and analysis.